Hall sensor systems using Hall switch arrangements are frequently used in the art for detecting positions, angular positions and distances of objects with regard to a Hall sensor element. Therefore, for example, a control magnet is brought close to a Hall sensor, so that a varying measurement voltage, e.g. Hall voltage, is generated at the same due to the varying magnetic field, which results due to the altered position and the altered distance, respectively. With the help of a downstream threshold evaluation circuit, e.g. a comparator circuit or a comparator circuit with hysteresis (Schmitt trigger circuit) the change of position can be detected in a digital way via control magnets. Thus, Hall sensors are used as so called Hall switch arrangement for position and distance detection, respectively, of_ movable parts. Hall sensor elements and Hall switches, respectively, are thus used particularly for the usage as position and proximity switches in industrial applications and particularly in the field of automobiles, wherein these Hall sensors can, for example, be used in a vehicle for detecting gear shift positions, the seat position, mirror positions, in the belt lock, in window regulators, in the sliding roof or other applications.
In the following, with regard to the Hall switch element 10 illustrated merely schematically in FIG. 4, its general mode of operation will be discussed below. As is illustrated in FIG. 4, the Hall switch element 10 has a first input terminal 10a for providing a supply voltage VCC, a second input terminal 10b for providing a reference potential GND, e.g. ground potential, and an output terminal 10c for providing an output signal OUT. Further, the Hall switch element 10 comprises a Hall sensor element 12, a control and supply means 14 and an evaluation and processing means 16. As illustrated in FIG. 4, the control and supply means 14 is provided to control the Hall sensor element 12 with an appropriate control signal and to further supply the evaluation and processing means 16, for example, with energy. The evaluation and processing means 16 is, for example, provided to evaluate the output signal, e.g. the Hall voltage, of the Hall sensor element 12, wherein the evaluation and processing means 16 is, for example, formed as a comparator means or a comparator means with hysteresis (Schmitt trigger) to output the output signal OUT to the output terminal 10c, which represents a switching state of the Hall switch element 10.
In the following, it will be explained with regard to FIGS. 5a–c, how a typical switching signal OUT of a Hall switch element is obtained. As illustrated in FIG. 5a, the Hall switch element 10 is, for example, subject to a magnetic flow density B with varying amplitude, wherein this represents, for example, the approximation or removal of a control magnet or generally any change of a magnetic field and a magnetic flux density, respectively, which penetrates the Hall switch element 10, and is based on a change of position of an object to be monitored. Then, in the Hall sensor element 12 of the Hall switch element 10, the magnetic flux density is converted into an output voltage proportional thereto, e.g. a Hall voltage.
If, for example, the evaluation and processing means is formed as simple comparator means with a switching threshold S0, the curve of the output signal illustrated in FIG. 5b results, wherein a change of the output voltage of the output signal is caused, for example between a first logic level “L” and a second logic level “H”, when the switching threshold S0 crosses the magnetic flux density and the resulting Hall voltage, respectively. A comparison of the magnetic flux density with the switching threshold S0 means that the output signal, i.e. the Hall voltage, of the Hall sensor element 12 is compared to a reference voltage as switching threshold.
In FIG. 2c, an output signal OUT is illustrated, which is obtained by a comparator means with hysteresis, wherein an upper threshold S1 and a lower threshold S2 are provided, wherein the output signal OUT when crossing the upper threshold S1 transits from the first logic level to the second logic level, and wherein the output signal OUT only transits back from the second logic level to the first logic level when the second lower switching threshold S2 is undershot. The first and second switching thresholds S1, S2 are, for example, disposed symmetrically around the basic switching threshold S0.
Through the hysteresis, it is achieved that for evaluation signals, which are fluctuating around the area of the switching threshold S0, no constantly changing output signal OUT is generated with every crossing of the switching threshold.
The output terminal 10c of the Hall switch element 10 is now generally connected to a microprocessor means (not shown in FIG. 4), which evaluates the switching signal OUT of the Hall switch element 10. As has already been mentioned above, such Hall switch elements 10 are, for example, used extensively in automobile engineering as position and proximity switches, respectively, wherein therefore, a plurality of switches are grouped relatively close in space to each other, for example for determining the gear shift position according to the number and resolution, respectively, of the positions to be detected. However, these Hall switch elements 10 are disposed relatively far apart from the microprocessor means, e.g. the board computer of a vehicle, which evaluates the switching state.
According to the prior art, an individual signal line is installed from every Hall switch element 10 to an individual microprocessor input. This provision of a plurality of lines to the microprocessor means represents an increased processing effort and thus increased processing costs. Further, it is required that the microprocessor means has sufficient input terminals for receiving every output signal OUT of every Hall switch element 10. If a large number of input terminals of a microprocessor means has to be provided, as a consequence, on the one hand, a relatively complex switching layout of the microprocessor means with a large number of input terminals will be required, and, on the other hand, the dimensions of the microprocessor means will have to be kept relatively large due to the large number of pins, since the size of a semiconductor chip is substantially influenced by the number of required pins.